The instant invention pertains to apparatus for setting a packer in a well bore and more particularly to such apparatus for setting packers of the type having a nonelastomeric packer element.
It may sometimes be necessary to seal the annulus between a tubing string and a well bore in a high temperature environment. Such may be necessary when injecting steam into a well bore, when producing from a steam flood well or from a fire flood well, or in thermal or geothermal recovery wells.
Such high temperature environments may exceed the thermal limitation of a conventional elastomeric packer element which is incorporated in a conventional packer. Prior art devices exist which are intended to seal a well annulus in a high temperature environment, e.g., U.S. Pat. No. 4,375,240 to Baugh et al. and U.S. Pat. No. 4,302,018 to Harvey et al. U.S. Pat. No. 4,281,840 to Harris and U.S. Pat. No. 4,441,721 to Harris et al. disclose high temperature packers and are assigned to the assignee of the instant application.
Harris '840 and Baugh et al. each disclose packers having non-elastomeric packer elements which are set by applying a longitudinal force thereto. Such elements may form a tight seal when the packer is initially set; however, thermal expansion of the metal portions of the packer, especially longitudinal mandrel expansion, gradually reduces the force applied to the packer elements and thus the strength of the seal.
The Harris '721 disclosure includes a plurality of Belleville springs 78 disposed between the lower end of the packer element and a setting piston which applies a longitudinal force to the spring and packer elements. The spring is intended to maintain the packer elements compressed as the mandrel lengthens as a result of thermal expansion and as the total length of the packer elements decreases as a result of melting or degradation of low temperature packer elements. It has been found that the Belleville springs do not have sufficient travel to maintain sealing action in the presence of high temperatures.
Moreover, the Harris, '840 and Harris et al. '721 disclosures do not provide a mechanism for setting slips independently of the packer elements. The instant invention provides an advantage over the prior art by providing apparatus which continuously exerts a biasing force against a packer element and which provides for independent setting of slips, with both the biasing and slip setting forces being generated by internal hydraulic pressure.
The instant invention comprises a mandrel having a nonelastomeric packer element disposed thereabout. Ratchet means are associated with the mandrel for moving the packer element toward a well bore when the apparatus is received therein. Biasing means continuously urge the packer element into sealing engagement with the well bore. Slip means are associated with the mandrel for setting the same in the bore and are set independently from the packer elements responsive to an increase internal mandrel pressure.